Long wavelength roughness optimization during thin Cu film electropolish

Recent studies of Cu electropolish indicate planarization is not possible due to a large diffusion layer thickness relative to a small post-electroplate step height and small Cu overburden available for electropolish. Assuming an integration scheme that includes a CMP step followed by electropolish, the subsequent challenge of maintaining surface roughness over 300 mu m range while electropolishing thin Cu films is addressed by optimizing applied current. For a typical electropolish solution of 6.4 M H(3)PO(4), 5.4 M glycerin and 17.5 M H(2)O, an rms value of 38 angstrom, comparable to the incoming post-CMP wafers, is demonstrated for 2500 angstrom Cu removal. (c) 2006 The Electrochemical Society.